There is an increasing need for storage of liquids in a subsea environment, particularly in the field of offshore oil and gas production. For example, liquid chemicals are used for enhanced oil recovery in which liquid chemicals are injected into subterranean hydrocarbon producing reservoirs to facilitate increased production of hydrocarbons from the reservoirs. In order for chemical injection operations to be most cost-effective, chemicals are needed to be stored on the seafloor in the vicinity of the subterranean hydrocarbon reservoirs.
For continuous or semi-continuous chemical injection for enhanced oil recovery to be possible, it is desirable that at least several days of chemical storage be provided. This could equate to very large storage volumes in order to match the injection rates. The majority of offshore oil and gas production existing facilities cannot accommodate such volumes. Offshore platforms cannot accommodate the space nor the weight associated with storage of such volumes. The installation of pipelines to transport the chemicals from shore is often not economically practical and in some areas can present environmental challenges. Floating production, storage and offloading (FPSO) vessels are another alternative means to supply the chemicals, but they are expensive to operate and can be sensitive to weather and ocean conditions.
There exists a need for apparatus, systems and methods for storing and managing liquids onsite in a subsea environment which address the aforementioned challenges in a cost effective, practical way.